Remove duplicate documentation

Author: bf4

docs/howto/test.md

@@ -10,20 +10,9 @@ class PostsControllerTest < ActionController::TestCase
   test "should render post serializer" do
     get :index
     assert_serializer "PostSerializer"
-    #  # return a custom error message
-    #  assert_serializer "PostSerializer", "PostSerializer not rendered"
-    #
-    #  # assert that the instance of PostSerializer was rendered
-    #  assert_serializer PostSerializer
-    #
-    #  # assert that the "PostSerializer" serializer was rendered
-    #  assert_serializer :post_serializer
-    #
-    #  # assert that the rendered serializer starts with "Post"
-    #  assert_serializer %r{\APost.+\Z}
-    #
-    #  # assert that no serializer was rendered
-    #  assert_serializer nil
   end
 end
 ```
+
+See [ActiveModelSerializers::Test::Serializer](../../lib/active_model_serializers/test/serializer.rb)
+for more examples and documentation.